FIG. 4 of the attached drawings shows the structure of corrugated cardboard of the prior art used as wrapping materials, etc. FIG. 4(a) is a plan view and FIG. 4(b) is the cross-section view of IV--IV of FIG. 4(a) The core cardboard (12) has a plurality of corrugations of waveshape (13) and on both sides of the core cardboard (12) has liner cardboard (14) which are glued to the crest portions of the corrugations (13). In some cases a liner cardboard (14) is only glued to one side of the core cardboard (12). The former is called two-side corrugated cardboard and the latter is called one-side corrugated cardboard. The material use for the core cardboard (12) and the liner cardboard (14) is pulp. The gap between the core cardboard (12) and the liner cardboard (14) is empty space (15). The corrugated cardboard having the structure described above is used as a wrapping material for electric appliances, etc., and serves the purposes of protecting goods as a cushion material from external shocks during shipping.
However, there is a problem or difficulty in wrapping around goods with the two-side corrugated cardboard.
Since the corrugations (13) are glued to both liner cardboard (14) it is difficult for either (14) to expand and shrink, when the corrugated cardboard is wrapped around an item, e.g. item 17 shown in FIG. 5. The inner liner cardboard (14) having a smaller bending radius has difficulty in bending in a circular shape between the corrugations (13) and thus tends to form a polygon shape bending at several places as shown in FIG. 5. For this reason, the corrugated cardboard (11) forms a gap with a goods (17) so that the goods (17) tends to drop from the corrugated cardboard (11).